Tweak new unification heuristic

1 files changed, 7 insertions, 4 deletions

diff --git a/src/elaborate.sml b/src/elaborate.sml
index 89c077e5..6556a8d6 100644
--- a/src/elaborate.sml
+++ b/src/elaborate.sml
@@ -865,12 +865,15 @@
 
          val (unifs1, unifs2) = eatMatching (fn ((_, r1), (_, r2)) => r1 = r2) (#unifs s1, #unifs s2)
 
-         val hasUnifs = U.Con.exists {kind = fn _ => false,
-                                      con = fn L'.CUnif _ => true
-                                             | _ => false}
+         fun isMappy (c, _) =
+             case c of
+                 L'.CApp ((L'.CMap _, _), c) => isMappy c
+               | L'.CUnif _ => true
+               | _ => false
 
          val (others1, others2) = eatMatching (fn (c1, c2) =>
-                                                  not (hasUnifs c1 andalso hasUnifs c2)
+                                                  not (isMappy c1 andalso isMappy c2)
+                                                  (* I guess this is a pretty bad hack, based on one pattern of bad unification I've seen! *)
                                                   andalso consEq env loc (c1, c2)) (#others s1, #others s2)
          (*val () = eprefaces "Summaries3" [("#1", p_summary env {fields = fs1, unifs = unifs1, others = others1}),
                                           ("#2", p_summary env {fields = fs2, unifs = unifs2, others = others2})]*)